Heat exchanger

ABSTRACT

A heat exchanger comprising a plurality of heat exchange plaques and plates stacked one by one to define coolant passage channels and hot passage channels to be cooled and configured to be crossed by a coolant fluid and by a hot fluid to be cooled. Each plaque is modular and comprises a first lateral plate configured to be positioned at the point where the hot fluid inlet opening and the coolant fluid outlet opening are located, and a second lateral plate configured to be positioned at the point where the coolant fluid inlet opening and the hot fluid inlet opening. Moreover, the lateral plates are connected to each other by respective connecting bars.

TECHNICAL FIELD

The present invention relates to a heat exchanger, particularly an exchanger of the “plate” type for the conditioning or the refrigeration of fluids.

BACKGROUND ART

Generally, the use of heat exchangers allows a heat transfer between a coolant fluid and a fluid to be cooled flowing inside adjacent passage channels and defined in the exchanger between several plates stacked onto each other and contiguous to each other. The channels are alternated with each other to allow heat transfer. The liquid passing through the plates is normally made to flow in cross-flow (counter-current) to increase the generated heat transfer, but parallel conformation (equi-current) is also possible.

Known exchangers, such as those disclosed for example in U.S. Pat. No. 4,815,534, are usually obtained by means of plates made in forming moulds and brazed together in vacuum and/or controlled atmosphere (CAB) furnaces. The moulds are therefore sized depending on the measurements required for the manufacture of the plates, which greatly limits the operational adaptability of the latter. In fact, it follows that plates made for a special exchanger cannot be used for different exchangers with even slightly different dimensions. Every slight variation in size and/or characteristics makes it necessary to invest heavily in new moulds, which limits the flexibility and production output of heat exchanger manufacturers.

DESCRIPTION OF THE INVENTION

The Applicant realized the need to develop a solution that would allow the production of extremely versatile plates for heat exchangers, adaptable to variable dimensions and therefore operable in any model of heat exchanger. In this way, the classic process of manufacturing plates has been completely modified, avoiding the need to make expensive and complex moulds.

The Applicant has thus designed a plate consisting of several parts which can be joined together and made by means of diversified processes that are on the whole cheaper than known construction processes, in order to free oneself from the constructional manufacturing dimensions, thus ensuring dimensional changes even of a few millimeters.

Therefore, the present invention relates to a heat exchanger according to claim 1 which enables to overcome the aforementioned drawbacks of the prior art in the context of a simple, rational, easy and effective to use as well as affordable solution.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a heat exchanger, illustrated by way of an indicative, yet non-limiting example, in the accompanying tables of drawings wherein:

FIG. 1 is an exploded perspective view of an exchanger according to the invention;

FIG. 2 is a front view of a plate according to the invention;

FIG. 3 is a view of a plate and a plaque in exploded configuration configured to manufacture a passage channel of a fluid to be cooled according to the invention;

FIG. 4 is a view of a plate and a plaque in an exploded configuration configured to manufacture a passage channel of a coolant fluid according to the invention;

FIG. 5 is an exploded perspective view in detail of two adjacent passage channels of fluid to be cooled/coolant fluid according to the invention;

FIG. 6 is a front view of a lateral plate according to a further embodiment of the invention.

EMBODIMENTS OF THE INVENTION

With particular reference to these figures, reference numeral 1 globally indicates a heat exchanger according to the present invention.

The exchanger 1 is provided with a plurality of heat exchange plates 2 and plaques 3 stacked one by one on each other along a stacking direction Y-Y. Conveniently, as shown in FIG. 1 , the plates 2 and the plaques 3 are located between a covering plate 6 and a base plate 7. Advantageously, the plates 2, 6, 7 and the plaques 3 are joined together tightly by means of a brazing process. Preferably, the covering plate 6 has four openings for the insertion of respective sleeves (not shown), in fluid communication by pairs for the inlet and the outlet of a coolant fluid C and a fluid to be cooled H.

In the volume space comprised between two adjacent plaques 3, respective coolant passage channels 4 and passage channels to be cooled 5 are defined which are crossed, respectively, by the coolant fluid C and the fluid to be cooled H.

Preferably, the fluid passing in the channel to be cooled 5 is oil while the fluid passing in the coolant channel 4 is water. The channels 4, 5 are arranged perpendicularly with respect to the stacking direction Y-Y while they result alternating with each other along said direction Y-Y.

With reference to the example illustrated in FIG. 2 , each plate 2 is advantageously made in a modular manner and comprises a first lateral plate 8 and a second lateral plate 9 connected to each other by means of a first connecting bar 10 and a second connecting bar 11.

Preferably, each lateral plate 8, 9 is made from an aluminum strip plated with low melting material and subsequently shaped, e.g. by laser cutting, to obtain a particular shape similar to a spectacle frame, as illustrated in the various examples attached in the figures.

In particular, each lateral plate 8, 9 has a closed contour ring portion 12 and an open contour curvilinear portion 13 joined together by a central connecting portion 14. The ring portion 12 has a through opening 15 while the curvilinear portion 13 is defined by a curvilinear extension 16.

Around the through opening 15 of the ring portion 12, there are a pointed upper portion 17, a curved lateral portion 18 and an enlarged lower portion 19 which serves as a base for the ring portion 12. At the connection area between the pointed upper portion 17 and the curved lateral portion 18 there is a housing 20 to receive, by shape coupling, one of the ends 11 a, 11 b of the second connecting bar 11.

With reference to the open contour curvilinear portion 13, the latter is also characterized by the presence of a pointed upper portion 21, substantially identical to the pointed upper portion 17 of the ring portion 12, and connected to the curvilinear extension 16. Conveniently, the curvilinear extension 16 ends up with a further housing 20 to receive, by shape coupling, one of the ends 10 a of the first connecting bar 10. In substance, the closed contour ring portion 12 differs from the open contour curvilinear portion 13 in the presence of the enlarged lower portion 19. In the examples of FIGS. 2-5 , the housings 20 have a substantially stepped shape by making an outwardly oriented containment space of the lateral plate 8, 9 for the housing of each upper end 10 a, 11 a, 10 b, 11 b. In particular, when each bar 10, 11 is joined to the respective housing 20, it makes with the lateral plates 8, 9 a linear continuity of shape with the extension 16 and the curved lateral portion 18, respectively.

According to a further embodiment shown in the example of FIG. 6 , the housings 20 of the lateral plates 8, 9 have a “U” shape to contain by interlocking and at least partly each end 10 a, 11 a, 10 b, 11 b of the bars 10, 11.

Further non-illustrated embodiments cannot however be ruled out wherein the housings 20 have different shapes always in order to achieve a stable coupling by shape with the respective ends of the bars 10, 11.

As shown in the example of FIGS. 3 and 4 , each plaque 3 has a coolant fluid inlet opening IC₍₃₎, a coolant fluid outlet opening OC₍₃₎, a fluid to be cooled inlet opening IH₍₃₎ and a fluid to be cooled outlet opening OH₍₃₎ collimated with the respective openings of additional plaques 3 to define:

-   -   coolant fluid inlet ducts IC,     -   coolant fluid outlet ducts OC,     -   fluid to be cooled inlet ducts IH, and     -   fluid to be cooled outlet ducts OH.

Preferably, the first lateral plate 8 is substantially identical to the second lateral plate 9. This makes the construction of the exchanger extremely simplified since it requires a single size of the lateral plates 8, 9. As can be seen, in fact, a same lateral plate 8, 9 may be rotated around the central connecting portion 14 and used so that its through opening 15 receives, depending on its positioning, the coolant fluid C and/or the fluid to be cooled H.

With reference to the embodiment of FIG. 3 , a plate 2 associated with a plaque 3 is shown wherein both are configured to make a passage channel to be cooled 5 of the exchanger 1. As can be seen, the through opening 15 of the lateral plate 8 is in fluid communication with the coolant fluid outlet opening OC₍₃₎ of the underlying plaque 3 while the through opening 15 of the lateral plate 9 is in fluid communication with the coolant fluid inlet opening IC₍₃₎ of the plaque 3. Similarly, each lateral plate 8, 9 of each plate 2 may be configured so that the through opening 15 collimates with a different coolant fluid inlet/outlet opening IC₍₃₎, OC₍₃₎ or with a different inlet/outlet opening of the fluid to be cooled IH₍₃₎, OH₍₃₎. In the embodiment of FIG. 4 , for example, a plate 2 associated with a plaque 3 is shown wherein both are configured to make a coolant passage channel 4. In this case, the through opening 15 of the lateral plate 8 is in fluid communication with the inlet opening of the fluid to be cooled IH₍₃₎ of the underlying plaque 3 while the through opening 15 of the lateral plate 9 is in fluid communication with the outlet opening of the coolant fluid OC₍₃₎ of the plaque 3. With reference to the example shown in FIG. 5 , two adjacent fluid passage channels are shown, operating in counter-current, wherein the passage channel of to be cooled 5 is positioned inferiorly to the coolant passage channel 4. In use, for each channel 4, 5, the volume for the passage of the fluids C, H, along the stacking direction Y-Y, is comprised between the upper surface of a plaque 3 positioned inferiorly, the inner sides of the bars 10, 11, the inner sides of the extensions 16 of each lateral plate 8, 9 and the lower surface of a plaque 3 positioned superiorly. In substance, the inner sides of the bars 10, 11 and the inner sides of the extensions 16 of each lateral plate 8, 9 form a modular frame for the flowing of fluids between them. It should also be noted that the direction of the fluids inside the channels 4, 5 may change depending on how the openings of the covering plate 6 are configured to receive at the inlet and at the outlet the coolant fluid C and the fluid to be cooled H. It is thus possible to arrange the channels so that they can operate either in counter-current or in equi-current depending on how the fluids C, H enter the exchanger.

According to an embodiment of the invention, each plate 2 may comprise a wire mesh 23 housed inside the volume comprised between two plaques 3 internally to the modular frame made by the inner sides of the bars 10, 11 and the inner sides of the extensions 16 of each lateral plate 8, 9. Advantageously, the wire mesh 23 is made from a press-formed strip and located inside the modular frame with the purpose of creating turbulence and facilitating heat exchange in the channels. Conveniently, the wire mesh 23 may be suitably shaped to follow the profile of the modular frame.

The Applicant has carried out several tests to verify the performance of the new exchanger according to the present invention.

An initial static pressure resistance test proved the complete sealing of the elements making up the exchanger. In particular, after brazing and before welding the connection sleeves, a test rig with a gasket system was used to ensure complete sealing and the exchanger was placed in a tank full of water. By applying pressurized air inside the exchanger, the absence of porosity and/or brazing failures was verified. For the test, the oil pressure in the channel to be cooled was brought up to 30 bar (required value 24 bar), while in the coolant channel the water pressure value was brought up to 6 bar (required value 3 bar). The same test was also repeated after welding the connection sleeves to ensure that the welding phase had not induced any damage to the brazing joints.

A second anti-mix test also showed that there were no leaks between the channels. In particular, the coolant channels were filled with water and the channels to be cooled with compressed air at a static pressure of about 5 bar. It has been verified that no bubbles escaped from the channels due to the passage of air. The test showed that even after previous tests there were no damage effects between the channels.

A further fatigue test at cyclic pressure according to the ISO 10771-1 specification allowed verifying the absence of leakage during predetermined stresses. The exchanger was able to sustain a cyclic operating pressure (between 0 and 16 bar) in the channel to be cooled with oil, with a frequency of about 2 Hz. The oil was brought to a lower temperature of 50° C. Although the standard requires the stress to be maintained for at least 1,000,000 cycles, tests carried out on the exchanger of the invention showed that at the 2,200,000th cycle no rupture was present.

Finally, a test was carried out to verify the heat transfer performance and pressure drop. Two fluids at different inlet temperatures (one at high temperature, the other at low temperature) were made to flow inside the exchanger, thus modifying the flow rates to determine any variations in heat exchange and construct a specific heat exchange power matrix. Also for this test, reduced and negligible pressure drop conditions (both of one fluid and the other) were recorded even with viscosity variations at certain operating flow rates.

It has in practice been ascertained that the described exchanger achieves the intended requirements and, in particular, the fact has been underlined that the manufacture of plates with variable modularity allows the adaptability to any model of exchanger even with dimensions extremely different in length. In addition, the manufacturing process of the lateral plates and of the bars has been greatly simplified, saving money while maintaining the exchanger's optimal performance and reliability. 

1. A heat exchanger comprising: a plurality of heat exchange plaques and a plurality of plates stacked one by one on each other along a stacking direction to define, in the space comprised between two adjacent plaques coolant passage channels and hot passage channels to be cooled arranged perpendicularly to the stacking direction and configured to be crossed by a coolant fluid and by a hot fluid to be cooled, respectively, wherein each plaque has a coolant fluid inlet opening, a coolant fluid outlet opening, a hot fluid inlet opening and a hot fluid outlet opening collimated with the respective openings of additional plaques to define coolant fluid inlet/outlet ducts of the and hot fluid inlet/outlet ducts for the fluids, wherein the coolant fluid inlet/outlet ducts and the coolant fluid inlet openings and the coolant fluid outlet openings are in communication with the coolant passage channel, the hot fluid inlet/outlet ducts and the hot fluid inlet openings and the coolant fluid outlet openings are in communication with the coolant passage channel, each plate is modular and comprises: a first lateral plate configured to be positioned at the point where the hot fluid inlet opening and the coolant fluid outlet opening are located, a second lateral plate configured to be positioned at the point where the coolant fluid inlet opening and the hot fluid inlet opening are located, and said lateral plates are connected to each other by means of respective connecting bars.
 2. The heat exchanger according to claim 1, wherein the first plate comprises an individual opening configured to be positioned coaxially to the respective coolant fluid outlet openings of the plaques for each coolant passage channel.
 3. The heat exchanger according to claim 1, wherein the second plate comprises an individual opening configured to be positioned coaxially to the respective coolant fluid inlet openings of the plaques for each coolant passage channel.
 4. The heat exchanger according to claim 1, wherein the first plate comprises an individual opening configured to be positioned coaxially to the respective hot fluid outlet openings of the plaques for each hot fluid passage channel.
 5. The heat exchanger according to claim 1, wherein the second plate comprises an individual opening configured to be positioned coaxially to the respective hot fluid inlet openings of the plaques for each hot fluid passage channel.
 6. The heat exchanger according to claim 1, wherein the first lateral plate substantially identical to the second lateral plate.
 7. The heat exchanger according to claim 1, wherein the inner sides of the bars and the inner sides of each lateral plate form a modular frame for the passage of fluids, each plate comprising a wire mesh housed inside the volume comprised between two plaques internally to said frame in order to create turbulence and facilitate the heat exchange in the channels.
 8. The heat exchanger according to claim 1, wherein each lateral plate comprises at least one housing to receive, by shape coupling, one of the ends of the connecting bars.
 9. The heat exchanger according to claim 1, wherein each lateral plate is shaped to obtain a shape similar to a spectacle frame.
 10. The heat exchanger according to claim 1, wherein each lateral plate made from an aluminum strip which is plated with low melting material. 